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This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

DESCRIPTION top

Thesymlink() function shall create a symbolic link calledpath2 that contains the string pointed to bypath1 (path2 is the name of the symbolic link created,path1 is the string contained in the symbolic link). The string pointed to bypath1 shall be treated only as a string and shall not be validated as a pathname. If thesymlink() function fails for any reason other than[EIO], any file named bypath2 shall be unaffected. Ifpath2 names a symbolic link,symlink() shall fail and seterrno to[EEXIST]. The symbolic link's user ID shall be set to the process' effective user ID. The symbolic link's group ID shall be set to the group ID of the parent directory or to the effective group ID of the process. Implementations shall provide a way to initialize the symbolic link's group ID to the group ID of the parent directory. Implementations may, but need not, provide an implementation- defined way to initialize the symbolic link's group ID to the effective group ID of the calling process. The values of the file mode bits for the created symbolic link are unspecified. All interfaces specified by POSIX.1‐2008 shall behave as if the contents of symbolic links can always be read, except that the value of the file mode bits returned in thest_mode field of thestatstructure is unspecified. Upon successful completion,symlink() shall mark for update the last data access, last data modification, and last file status change timestamps of the symbolic link. Also, the last data modification and last file status change timestamps of the directory that contains the new entry shall be marked for update. Thesymlinkat() function shall be equivalent to thesymlink() function except in the case wherepath2 specifies a relative path. In this case the symbolic link is created relative to the directory associated with the file descriptorfd instead of the current working directory. If the access mode of the open file description associated with the file descriptor is not O_SEARCH, the function shall check whether directory searches are permitted using the current permissions of the directory underlying the file descriptor. If the access mode is O_SEARCH, the function shall not perform the check. Ifsymlinkat() is passed the special value AT_FDCWD in thefd parameter, the current working directory shall be used and the behavior shall be identical to a call tosymlink().

ERRORS top

These functions shall fail if:EACCESWrite permission is denied in the directory where the symbolic link is being created, or search permission is denied for a component of the path prefix ofpath2.EEXISTThepath2 argument names an existing file.EIOAn I/O error occurs while reading from or writing to the file system.ELOOPA loop exists in symbolic links encountered during resolution of thepath2 argument.ENAMETOOLONG The length of a component of the pathname specified by thepath2 argument is longer than {NAME_MAX} or the length of thepath1 argument is longer than {SYMLINK_MAX}.ENOENTA component of the path prefix ofpath2 does not name an existing file orpath2 is an empty string.ENOENTorENOTDIR Thepath2 argument contains at least one non-<slash> character and ends with one or more trailing <slash> characters. Ifpath2 without the trailing <slash> characters would name an existing file, an[ENOENT]error shall not occur.ENOSPCThe directory in which the entry for the new symbolic link is being placed cannot be extended because no space is left on the file system containing the directory, or the new symbolic link cannot be created because no space is left on the file system which shall contain the link, or the file system is out of file-allocation resources.ENOTDIR A component of the path prefix ofpath2 names an existing file that is neither a directory nor a symbolic link to a directory.EROFSThe new symbolic link would reside on a read-only file system. Thesymlinkat() function shall fail if:EACCESThe access mode of the open file description associated withfd is not O_SEARCH and the permissions of the directory underlyingfd do not permit directory searches.EBADFThepath2 argument does not specify an absolute path and thefd argument is neither AT_FDCWD nor a valid file descriptor open for reading or searching.ENOTDIR Thepath2 argument is not an absolute path andfd is a file descriptor associated with a non-directory file. These functions may fail if:ELOOPMore than {SYMLOOP_MAX} symbolic links were encountered during resolution of thepath2 argument.ENAMETOOLONG The length of thepath2 argument exceeds {PATH_MAX} or pathname resolution of a symbolic link in thepath2 argument produced an intermediate result with a length that exceeds {PATH_MAX}.The following sections are informative.

APPLICATION USAGE top

Like a hard link, a symbolic link allows a file to have multiple logical names. The presence of a hard link guarantees the existence of a file, even after the original name has been removed. A symbolic link provides no such assurance; in fact, the file named by thepath1 argument need not exist when the link is created. A symbolic link can cross file system boundaries. Normal permission checks are made on each component of the symbolic link pathname during its resolution.

RATIONALE top

The purpose of thesymlinkat() function is to create symbolic links in directories other than the current working directory without exposure to race conditions. Any part of the path of a file could be changed in parallel to a call tosymlink(), resulting in unspecified behavior. By opening a file descriptor for the target directory and using thesymlinkat() function it can be guaranteed that the created symbolic link is located relative to the desired directory.

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online athttp://www.opengroup.org/unix/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, seehttps://www.kernel.org/doc/man-pages/reporting_bugs.html .IEEE/The Open Group 2017SYMLINK(3P)